1. Field of the Invention
This invention relates to a Hookes joint which is a joint usable between shafts permitting rotational drive to be imparted from one shaft via the joint to another shaft whilst permitting variation of alignment between the driving and driven shafts. A Hookes joint comprises a cross member and two yokes, one of which yokes is typically connected to a driving shaft and wherein the other yoke is typically connected to a driven shaft such as in, for example, a vehicle propeller shaft drive train or in a power take-off drive train of an agricultural tractor. The cross member has four radially extending journals arranged in two pairs thereof, the journals in each one of said two pairs being coaxial with one another and the axes of the two pairs of journals being perpendicular to one another, the journals of one said pair thereof being rotatably mounted in bearing assemblies in corresponding ends of one said yoke and the journals of the other said pair thereof being rotatably mounted in bearing assemblies in corresponding ends of the other said yoke.
2. Description of Prior Art
Lubrication of the bearing assemblies within the joint has been proposed to be accomplished by the provision of bores within the cross member journals for the distribution of lubricant out of the open ends of the bores to the bearing assemblies. It has been proposed to distribute lubricant to the bearing assemblies via a single lubricant nipple on the cross member which communicates internally of the cross member with all of the bores in the journals. For example, in DE-A No. -28 41 955 it has been proposed to connect the four lubricant bores in series relationship by appropriately arranged conduits within the cross member in such manner that lubricant can be fed from a single lubricating nipple in series from one bearing assembly to another.
In such an arrangement, the means for distributing the lubricant is complex and requires the incorporation of various conduits and closure means resulting in a joint which is expensive to manufacture. Furthermore, such a distribution of lubricant in series from one bearing assembly to another cannot readily result in uniform supply of lubricant to each bearing assembly. The arrangement also suffers from a disadvantage that plugs or clots of dried lubricant may constrict the lubricant bores thus further reducing uniform distribution of lubricant to the bearing assemblies.